Sheet stacking mechanism



Aug. 4, 1953 Filgd June 6. @949 A. F. PIERCE SHEET STACKING MECHANISM 6Sheets-Sheet 1 IT H f n 1| 74 /v 46 46 W 1 In 56 l 66 50 g l I INVENTOR.ALFRED FRANK PIE/ace- 70 V ATTORNEYS 1 72 REYNOLDS a BEACH BYM/CJM 4,1953 A. F. PIERCE 2,647,645

SHEET STACKING MECHANISM Filed June 6, 1949 6 Sheets-Sheet 2 E JNVENTOR.

7 ALFRED FRANK PIERCE ATTORNEYS REYNOLDS 5 BEACH M/a): M

Aug. 4, 1953 A. F. PIERCE 2,647,645

SHEET STACKING MECHANISM Filed June 6, 1949 6 Sheets-Sheet 3 IN VEN TOR.

ALFRED F'KA NK PIERCE I ATTORNEYS H REYNOLDS & BEACH H BYW/MM 4, 1953 A.F. PIERCE 2,647,645

SHEET STACKING MECHANISM Filed June 6, 1949 e Sheets-Sheet 4 N q X l b oI N VEN TOR.

ALF/e51: FRANK PIERCE ATTORNEYS REYNOLDS a: BEACH BYW/QJE W Aug. 4, 1953A. F. PIERCE SHEET STACKING MECHANISM 6 Sheets-Sheet 5 Filed June 6,1949 INVENTOR ALFRED F'EANK PIERCE ATTORNEYS REYNOLDS & BEACH Aug. 4,1953 A. F. PIERCE SHEET STACKING MECHANISM 6 Sheets-Sheet 6 Filed June6, 1949 ///.fi/v// WNW //v/// @P ww iv 3 ow JNVENTOR. ALFRED F'RANKPIERCE ATTORNEYS REYNOLDS & BEACH BY WWW Patented Aug. 4, 1953 SHEETSTACKING MECHANISM Alfred Frank Pierce, Tacoma, Wash., assignor toAmerican Manufacturing Company,

Inc.,

Tacoma, Wash., a corporation of Washington Application June 6, 1949,Serial No. 97,411

11 Claims. (01. 214-6) In modern plywood factories presses of themulti-platen type, because of their large load capacity, are used almostuniversally for binding the plywood panels. In this type of press thepanels bonded are not arranged in a solid column or stack but areseparated, individually or in groups, by a series of press platenssuppotring them, which can then apply heat directly to the individualpanels for activating the bonding adhesive used. Preferably unloading ofthe press is accomplished by discharging the entire load of panels as asingle group by sliding them edgewise off the press platens and intoopen shelves of a receiving rack stationed adjacent to the offbear sideof the press. This unloading technique enables putting the press back towork immediately on a fresh load of panel stock, whereas the receivingrack can be unloaded and the panels stacked during the ensuing periodwhile the press is in operation.

In the past the unloading and stacking of panels from the rack has beenmanual. However, as they were rather inconveniently disposed in the rackto be grasped and removed by hand, and are usually too large and heavyfor one man alone to handle, this unloading and stacking operationrequired virtually the full time of two men working as a team.

My present invention relates to a method and to novel apparatusoperating automatically in removing the panels from the receiving rackand stacking them in a desired location for removal by a lift truck orsimilar conveyance. The invention includes, among various features, themethod, the automatic stacker, and the combination of such an automaticstacker and a re ceiving rack cooperating therewith, the whole occupyinga minimum of floor space.

As a further object the stacking apparatus is compact, reliable inoperation and comparatively inexpensive to manufacture and maintain.Moreover, it operates rapidly, so that there is no delay betweenreadiness of the press todischarge a load of panels into the rack andcompletion of the operation of unloading the precedingbatch of panels. v

Still another and more specific object is to overcome the evidentphysical problem of withdrawing the expansive, heavy, yet flimsy,horizontally disposed panels from between the narrowly spaced shelveswhich they occupy in the raclgand transfer them to the top of a stackwith minimum lost motion and delay. There are complications in doingthis in that the stack grows progressively from zero to a selectedheight.

Moreover, the panels emerging successively from the rack shelves must doso at the different heightsof such shelves. It is obvious that if theemerging end of a panel or panel group were allowed, unsupported, todroop increasingly in process of emerging from a rack space, thetrailing end of the panel or group would eventually spring upwardagainst the rack shelf above it, halt the movement of the panel orgroup, and possibly cause damage. It is therefore evident that thepanels cannot simply be ejected haphazardly from the rack shelves, andallowed to drop as they may. v

In light of these circumstances my invention comprises novel panelunloading and stacking apparatus having a-djus'tably elevated conveyormeans cooperating with the receiving rack and operable to move thepanels one after another edgewise from the rack shelves in successiveorder, preferably commencing with the lowermost and progressing to theuppermost panel on the rack, into position for deposit on top of thestack of panels being formed. Coacting with such conveyor means is apanel stacking plat form disposed adjacent to the rack and automaticallyadjusted in its elevation differentially in relation to the panelconveyor means, to maintain the top of the stack at all times justslightly below the changing elevation of the emerging panels. f

Preferably such elevated transfer conveyor means is of the continuousbelt or similar type, and comprises a horizontal row of belt conveyorswhich extend lengthwise of the rack into its shelf spaces to engage thebottom faces of the panels, lift them off their respective shelves andtransport them edgewise therefrom to the stack, successively. In. orderto permit these conveyor elements to enter the rack spaces to engage andremove the panels in that manner, and to allow the conveyor elements tobe elevated directly through the rack progressively from the level ofone rack shelf to another, the rack shelves are constructed in specialcantilever fashion.

A further feature of the invention resides in the provision of elevatormeans carrying both the ,conveyor means and the stack-supportingplatform, the latter being carried by a jack which is preferably of thehydraulic type and valve-controlled automatically in response tooperation of the conveyor means transferring successive panels from therack to the stack being formed on such platform. In the illustrated andpreferred case the valve-controlled loaded hydraulic jack isintermittently released to descend by 9 grawlty an incremental amountrelative to the conveyor means, such amount corresponding approximatelyto the thickness of a panel or group of panels carried by one shelf ofthe loader, each time a panel or panel group is transferred to the stackon the platform. More particularly, the control valve which permits thisincremental descent of the hydraulic jack is preferably controlled bymechanically actuated switch means set to open the hydraulic reliefvalve with the reception of each new panel or panel group on the top ofthe stack, and to close such valve auto matically after the stack hasdescended a distance approximately equal to the increased height of thestack.

These and other features, objects and advantages of the invention willbe understood better by reference to the following more detaileddescription and the accompanying drawings.

Figure 1 is avertical sectional view of the combination stackingmechanism and receiving rack, taken transversely thereof on line :|-l inFigure 3, part of the rack, shown in broken lines, being broken away;Figure, 2 is a similar view showing the stacking mechanism in adifferent operating position. Figure 3 is a horizontal sectional view ofthe same taken on line 33 of Figure 1.

Figure 4 is a horizontal sectional View of the stacking mechanism takenon line l-fi in Figure 1, parts, such as of the panel conveyor elements,being broken away for convenience in illustration.

Figure 5 is an enlarged detail of a portion of the stacking mechanismand receiving rack as shown in Figure 2.

Figure 6 is an end elevation View of the stackingrnechanismfrom its sidefacing the receiving rack.

Figure 7 is a detail view of limit switch mechanism shown in Figure 6.

Figure 8 is a side elevation view of the receiving shown in Figure 8,are designated .P in other 7 figures. The invention itself residesbroadly in the method of handling the panels after their discharge fromthe press into the receiving rack, andin the combination receiving rackand stacking mechanism implementing such method. However, the inventionis not limited in its application to the handling of plywood panels orto thehandling of plywood panels received from a multiplaten bondingpress, but extends to any similar type of situation involving thehandling of panels or similar objects forstacking purposes generally.

The multiplaten plywood bonding press illustrated in Figure 8 is ofconventional form, generally comprising a stationary head or upper pressblock I 6 supported by standards It, a lower reciprocable press block orram 20, usually hydraulically actuated, and a plurality of workseparating platens 22 arranged in series between the upper block [6 andram 2!]. The press is loaded by inserting stock for one or more panelsbetween each successive pair of platens 22 which are separated typicallyabout three inches to receive the stock when the press is open. Thehydraulic ram 26 is then raised to pick up the lowermost platen 22carrying panel stock, then the next successive platen and the next,progressively, one platen resting on the other ith the plywood panelstock interposed therebetween, until the press platens 22 and panelstock form a solid column which is pressed to the desired degree by ram29, forced against press block it for the requisite bonding period. Atthe same time, heat may be applied to the panels by the press blocks andindividual platens to activate the bonding adhesive used.

When the press is opened by descent of the ram 26 to restore theoriginal three-inch spacing between platens 22 the panels are dischargedfrom the interplaten openings by suitable means (not shown) into thewaitin' receiving r oi; l2 stationed adjacent to the The height of atwenty opening press when open, between block 55 and ram 2t, may be inthe vicinity of ten for example. This means that the receiving rack itmust be of corresponding height, as the individual rack shelves 2 5 mustlie rohmately in horizontal registry with the individuai press platens22 to which they correspond the panels are to be transferred from thepress to the rack by simply moving them horizontally edgewise, which isthe preferred method.

With a receiving rack in the vicinity of ten feet in height above floorlevel, and with plywood panels four feet by eight feet and larger, ingroups perhaps as much as two inches thick, carried by the shelves ofthe rack to its full height, one may readily appreciate the diflicultyof taking the panels out of the rack and stacking them when donemanually. By the present invention the receiving rack is constructedspecially and cooperates with novel mechanism which automaticallyunloads the rack and stacks the panels. All of this is done in the fewminutes between the time the press closes on a succeeding batch ofpanels and later opens with those panels freshly bonded and ready to bedischarged into the receiving rack.

While various details of the rack 12 are entirely optional in form,there are certain features about it which are important according to thepractice of my invention. Of importance is the general construction ofthe rack shelves and the general manner in which they are supported fromthe rack framework. The rack framework itself is subject to considerablevariation and consists in the present case of a base 2% and uprightrec-- tangular side frames 28 braced by diagonal mem-- bers 3i!connected to the base. For considerations of convenience not hereimportant the base 25 has wheels 3?. at its four corners which ride onsupporting rails 3d, extending lengthwise between the press and thestacking mechanism I l.

One vertical side of each rectangular rack frame 28 is situated at theend of the rack nearest the press iii. The other and parallel side ofeach such frame is situated generally intermediately between that endand the opposite end of the receiving rack. Between these vertical sidemembers of the rectangular frame 223 on opposite sides of the rackextend a plurality of structural members 36, such as angle iron or thelike, arranged horizontally and at vertical intervals corresponding tothe spacing between platens 22 of the press I0 when the press is open.If the press with which the receiving rack is to be used accommodatestwenty plywood panels, then there will be at least twenty of thesehorizontal structural members 36 in each of the two vertical rowsbridged between elements of the opposite frames. Thesehorizontalstructural members 36 constitute supports for individual rack shelves orform a part thereof. Preferably such shelves are constructed in themanner herein illustrated (see Figures 8 and 3), comprising one or morelongitudinal members 38 extending substantially the full length of therack between its ends adjacent to the press and the stacking mechanismi4, respectively. The longitudinal members 38 in each shelf are spacedapart widthwise of the rack at suitable intervals for a purpose to beexplained later herein.- They are each connected to the two horizontalstructural members 36 of the rack for such shelf, and project cantileverfashion a substantial portion of their length from their intermediatepoint of support, namely, on the intermediately'located structuralmember 36, toward the end of the rack adjacent to the stacking mechanisml4. 1 v

As much as one-half or more of the total length of members 38 mayproject in this manner, their free ends not being connected in anymanner to each other or to any other part of the rack, so that endwiseof the rack, viz. from press I!) to stacking mechanism I4, the shelfspaces are completely open throughout, and heightwise the rack issimilarly unobstructed in that portion of its length between theprojecting ends of the cantilever shelf members 33 and their generallyintermediate p-oints of support. Preferably the number of suchlongitudinal members included in each rack shelf is no greater thannecessary, and they are distributed, to provide ample support to thefreshly bonded plywood panels discharged from the press, withoutexcessive sagging of the panels between supporting rack elements.

The panels moving from the press onto the rack shelves cannot moveedgewise far out of line laterally because of the presence of therectangular side frames 26 of the rack, which serve as retainer guides,although they will usually not be contacted by the panels. Each of thelongitudinal shelf members 38 carries a plurality of rollers 46 tosupport the panels and minimize fric-- tion in sliding the panels on andoff the rack shelves The shelvesare in the illustrated case of suchproportions that the longitudinal dimension of the panels supportedthereby extend widthwise of the rack, so that a long edge of the panelis its leading edge in moving through the rack from thepress toward thestacking mechanism l4.

The stacking mechanism includes a plurality of generally horizontalconveyors 42, preferably of the belt type, arranged substantially inhorizontal registering and carried for bodily movement up and downthrough the open spaces between the cantilever elements 63 comprisingthe rack shelves. As shown in Figure 3, four of these conveyors areemployed, located at intervals across the width of the receiving rackI2, Their function is to engage the underside of a panel P or a group ofpanels on a rack shelf and transfer the panel or panel group from suchshelf to the top of a stack S of panels being formed by the stackingmechanism, as will be explained. Generally these conveyors 42 extendlengthwise of the rack far enough into the rack shelf spaces so thatwhen they engage the underside of a panel and lift it from the rack theconveyor beltswill carry a sufficient'part of the total weight of thepanel and'contact a sufficient surface area thereof to draw the panelfrom its remaining supporton the shelf and set it into motion on the-conveyor belts toward the stack. These conveyors 42 are mounted on theside of an elevator cage or frame 44 to project cantilever fashion intothe rack shelf spaces, interdigitated with the cantilever shelf supports38 (Figure 3), and to be moved up and down by such elevator.

The stacking mechanism also includes a panel stacking platform 46carried by a jack 48 which in this case is preferably a hydraulic jackmounted directly in the base of the elevator frame 44, as shown (Figure1). Initially the stacking platform 46 is positioned by the hydraulicjack 48 on the elevator frame slightly below the level of the beltconveyors 42. When the stacking operation is to be commenced, the beltconveyors, thus positionally related'to the platform, are disposedby'the elevator in their lowermost position, name- 1y, beneath thebottom panel or panel group P in the loaded rack. The conveyor belts arethen started and the elevatorc-arrying the conveyors, the stackinplatform and jack, gradually raised until the conveyor belts engagefirst the panel loaol in the bottom rack space, then that in thematically reversed and the entire elevated mechanism lowered until theconveyors have descended to their initial positions at the base of therack ready for commencing the unloading of the next batch of panelstherefrom.

.During the time the conveyors re ascending through the rack spacessuccessively to unload the panels the stacking platform 46 supported bythe jack lfi is being lowered by increments on the elevatorframe inrelation to the conveyors, so that as the growing stack of panels on theplatform increases in height, the top of such stack will nevertheless bemaintained at a level always slightly below that of the ascendingconveyors.

Thus, the panels transferred by the conveyors do not have to drop ortilt downward appreciably in coming to rest onthe stack. Moreover, thetop of the stack will never be so high as to obstruct such transfer.After the stack has grown to the desired size, perhaps comprising two orthree press loads of panels, it may be removed from the stackingplatform by a lift truck or similar conveyance and a new stackcommenced. At that time the stacking platform is restaged in relation tothe conveyors so that the platform will again be located only slightlybelow the level of the conveyors, preparedto receive the lowest panel inthe receiving rack. I

Having in mind these general features of the apparatus certain otherdetails of construction and operation of its illustrated form will nowbe explained. Because it isusually convenient to mount the press and tosupport the receiving rack at'fioor level, it is necessary to mount theelevatormechanism on. a sub-floor 56 (Figure l). The elevator frameconsists of four corner posts 52 whichextend from the sub-floor 56 to aheight somewhat above the top of the receiving rack and serve as guidesfor travel of the elevator frame 44 and stacking platform 46 movabledifferentially in relation to such frame. At its top the elevatorframework is comp-leted by a suitable girder str1ict1ire54 which spansbetween the four posts to constitute a support for the elevator hoist-mechanism'.- 'I'he-- latterin'cludcs an, electric motor drive unit 56(Figures land 6 connected by'a chain and sprocket transmission to acentral drive shaft 58 which rotates two cable drums 60, one at eachend. At the four corners of the top'of' the elevator framework arelocated cable guide sheaves 62, over which run the hoist cables E4connected to the corners of the base of the elevator cage, as shown inFigures 1 and 6, for example. The hoisting mechanism as such is ratherconventional and should require no further description.

The minimum height dimension of the elevator frame or cage 44 betweenits base 56 and the mounting'location thereon of the conveyors 42 isgoverned primarily by the desired maximum height of a stack of panelstobe accumulated on the stacking platform 45. The length of the barrel orcylinder 58 of the hydraulic jack 48 will be governed by substantiallythe same considerations. This hydraulic cylinder, mounted on theelevator projects downwardly therefrom and is accommodated in asub-floor pit Ill in the lowered position. of the elevator 44. Thecylinder is of the single-ended type, having a fluid conduit connection'52 (Figure 1) only at its bottom end and asolenoid actuated controlvalve I 30 in such fluid conduit to control actuation of the hydraulicpiston 14 cooperating with such cylinder, whereby to establish theheight of the stacking platform on the cage 44 and in relation to theconveyors 42.

The details of the stacking platform 46 and the elevator frame or cage44 are not especially pertinent to an understanding of the invention.Suffice it to say that the elevator, the stacking platform, and the baseof the elevator cage are suitably constructed to carry their respectiveloads, and are suitably guided for vertical travel on the corner guideposts 52. On its end remote from the receiving rack the stackingplatform preferably carries two or more upright rods I6 which serve asstops for the panels sliding across the top of the stack being formed onthe platform, carried by momentum from the belt conveyors 42 to theirrest positions on the stack. At its end adjacent to the receiving rackthe elevator cage embodies a vertical framework 18 (Figure 6) whichsupports the belt conveyors and certain other mechanism near its upperend, and which has suitable slide elements 80 (Figure 8) at each end bywhich it is guided from cornerposts 52 for vertical travel.

The upper end of this framework I8 carries projecting arms '82 whichactuate slide rods 84 for movement up and down with the elevator. Theupper ends of these slide rods telescope within cylindrical guide tubes86 supported from the ceiling and braced laterally from the elevatorframework, as shown (Figure 1). These rods serve as stops to preventpanels discharged from the press into the rack overtraveling the rackshelves by momentum in the direction of the stacking mechanism. They donot interfere with transfer of the panels from the rack to the panelstack by belt conveyors 42 because their lower ends are maintained ashort constant distance above the tops of the conveyor belts to clearthe panels thereon, and because the rod-supporting arms 82 are mountedon and move vertically with the conveyor-supporting framework 18.

As shown in Figure 6, this portion 18 of the elevator cage or frame 44carries at its top an electric motor drive unit 88 connected by atransmission chain and sprocket, encased in a guard 99, to acountershaft 92 which extends th width of such elevator frame portion,and is journaled thereon. This countersliaft rotates belt conveyor drivepulicys 94 (Figure 5) in each of the respective belt conveyors 42. Asshown best in this figure, each belt conveyor additionally includes aguide sheave 96 journaled at the outer end of a supporting arm 98 whichis pivotally supported on the elevator cage framework 18 by pivot 99 forswinging about a horizontal axis defined thereby. This arm carries asecond belt guide sheave I06 at an intermediate location between pulleys94 and '96. The conveyor belt Hi2 passes around all three of thesesheaves which locate its upper stretch appreciably above the top of thearm or any other puts carried-thereby which might tend to interfere withfree movement of the panels carried by the belts. Belt tension ismaintained oradjusted by providing the guide sheave with an adjustablejournal support IM to establish its position lengthwise of the arm.

The arm fit is mounted pivotally on pivot 99 in the manner described asa protective or safety feature. In the absence of special. provision,should a panel being transferred from the rack to the stack on theelevator platform by the belt conveyors be interrupted for any reasonand fail to move clear of the rack before the progressively ascendingbelt conveyors 42 raise the panel so far as to contact the rack shelfnext above, there will bea complete blockage in operation of thestacking mechanism because the stopping of the panel in thatintermediate position will check further ascent of the elevator. Thespecial provision which circumvents any such possibility comprisesyieldable supports for the pivoted belt conveyor arms which normallyhold such arms generally level, but which can yield if necessary toallow for some additional ascent of the elevator cage even after a panelbecomes caught between a rack shelf and the belt conveyor in the mannerpreviously indicated, without damage to the mechanism as a whole. Theyieldable support for a cantilever conveyor arm (Figure 5) comprises-aspring H16 reacting upwardly against the arm from a support bracket 03to maintain the arm normally in horizontal position projecting itsconveyor belt endwise into the receiving rack. The arms position may bevaried by means of a support iii} adjustable for raising and loweringthe base end of the spring as desired.

In addition, the precautionary support construction of the beltconveyors includes a safety switch H2 arranged to be actuated byexcessive downward deflection of a conveyor arm in the event of a panelP being caught between the belt conveyor and the rack shelf next abovethe panel, as shown in Figure 5. This switch H2 is included in theenergizing circuit (not shown) for the elevator hoist motor 55;preferably also in the energizing circuit for the belt conveyor motor88. The motor-energizing circuits may be conventional and need noillustration herein.

The switch may include a control lever I M actuated by an arm H6 whosebase end is pivoted on a-supporting bracket l I 8. This actuating arm isdepressed by a rod or bolt iiill interconnecting the same with theconveyor arm 98 so that as the latter is forced to swing down by apredetermined amount relative to the elevator cage, the actuating arm Iit releases the lever I l of switch H2, which is spring-pressed towardopen position and deenergizes the electric motors operating the stackingmechanism. Preferably each of the four belt conveyors and sup-portingparts thereof have similar switch mechanism since it is possible thatblockage of the ascent of only one of the belt conveyors may take placewhile the others are free to rise, and it will be just as desirable tostop the motors in that event as in the case where all are blocked. a I

A greater degree of positveness in the conveyance or transfer of panelsfrom the rack to the stacking platform is obtained by provision ofarm-supported driven hold-down rollers I32, shown in Figures 1 and 2,which press the panel or panel group down against the belt conveyors I82and cooperate with such conveyors in moving it, after being moved farenough from the rack to pass beneath such rolls. These rollers arebelt-driven from pulleys I46 on a countershaft I34 (Figure 6), driven bythe same chain mechanism which drives countershaft 92 from drive unit88. Such countershaft also serves as thesupport for arms I36 which carrythe rollers I32. These arms are free to swing downward toward theirrespective belt conveyors I82, being journaled on shaft I34, but arelimited in their downward displacement so that the rollers I32 cannotactually contact or wedge past the conveyor-belts beneaththem, althoughthey can readily press against the top of a panel resting on such belts.Their lowermost positonis established by an adjustable stop I38 (Figure2 The arms are swung downward aflirmatively and their rollers I32 forcedagainst the panel, producing a firm grip on the panel when being transferred, by virtue of the torque applied to the arms as an inherentresult of the turning of the belt drive pulleys I46 which drive theroller drive belts I42. Such rotation of the arms is resisted by a panelon the belt conveyors I62, or by the stop I38 when no panel isinterposed between the conveyors 42 and the rollers I32.

The upper end of the elevator cage or frame 44 also carries a bracketI2I, shown in Figure 2, to which a control arm I22 is pivotallyconnected. This swingable arm extends laterally over the stackingplatform 46 and carries a roller I24 at its swinging end, which isadapted to rest directly on top of the stack of panels being formed onthe stacking platform. The supported end of the-arm is arranged toactuate a switch I 26 which operates the solenoid valve I 36 (Figure,1). Thearm has a normal position in which such switch is open and thesolenoid valve closed to prevent discharge of hydraulic fluid from thecylinder 68, and thereby maintain at a constant elevated position thejack and stackng platform relative to the elevator cage. However, if thearmis raised slightly, namely,- by the thickness of a panel, from thisnormal position, it closes the switch I26 which opens the solenoid valveI30 to allow discharge of hydraulic fluid from the cylinder, enablingthe platform to descend by its own weight on the jack.

As the platform descends the arm I22 resting on the stack of panelsswings downward, and after its swinging end has descended an amountapproximately equal to the increase in height of the panel stack theswitch I26 is again opened and the discharge of fluid from the cylindercut off. It will therefore be evident that each time a panel or panelgroup moves from the belt conveyor onto the stack and slides beneath theroller I24 it raises the swinging end of arm I22 to close the valvecontrol switch I26, and initiates descent of the jack. By ths means thetop of the stack of panels on the stacking platform 46 is alwaysmaintained slightly below the level of the belt conveyors, as desired.

The upper and lowerlimits of travel of the ele-' vator cage and beltconveyors carried thereby are established by means of limit switchmechanism illustrated in Figures 6 and '7. Such mechanism includes aswitch control rod I44 extending generally the height of the elevatorstructure. The weight of this rod is carried at its upper end by supportmeans including a switch box I46 having apertures through which the rodis guided for limited vertical displacement, and a spring I48 reactingagainst a fixed collar I50 at the upper end of the rod to urge such rodnormally into anupwardly displaced position. Inside the switch box I46the rod carries a cam sleeve I52 constituting a switch-actuatingelement. Two switches are arranged inside the switch box, an upperswitch I54 arranged to be actuated by the sleeve I52 upon upwardmovement of the rod I44 to, reverse the electric motor operatingthehoist mechanism, and a lower switch I56 arranged ,to be actuated bysuch sleeve I52 to stop the hoist motor by downward displacementof suchrod. The straight portion of the rod depending from the switch boxcarries thereon two fixed collars, an upper collar I58 and a lowercollar I68, spaced apart by the desired length of travel of theelevator. The base of the elevator cage has an element I62 whichprojectslaterally therefrom to slide over the section of rod I44, between thesecollars, and raise and lower the rod by contacting the collars I58 andI60, respectively.

During ascent of the elevator cage, when the abutment element I62strikes the upper fixed collar I 58 it thereby raises the control rodI44, which trips the switch I54 and reverses the electric motor drivingthe hoist mechanism, to cause the elevator to descend. When the elevatorcage approaches the desired lowermost position this abutment strikes thefixed collar I66 and, against the force of spring I48, depresses thecontrol rod I44 to actuate the switch I56 and stop the hoist drivemotor. The drive motor can then be started again only by external means,such as bya separately controlled switch of thepush-button type whichwill be depressed momentarily by hand at a desired later time, bypassingthe switch I56 in a suitable hoist motor energizing circuit, until theelevator cage has ascended again sufficiently to break the engagement ofabutment I 62 with collar I60 which has been held depressed by theabutment to hold switch I56 open. It will be obvious that various othercontrol arrangements, could be utilized to control stopping and startingof the elevator and to limitits vertica1 travel in either direction.

As an added precaution, or in lieu of limit switches I54 and I56, I mayprovide an additional limit switch I64 (Figure 4), the same to be drivenby a chain I66 synchronously with the hoist drive shaft 58. The switchI64 amy be so constructed and arranged that after a predetermined numberof rotations of hoist drive shaft 58 in one direction or the other tothe desired extremepositions of corresponding travel of the elevatorcage 44, the switch will operate to reverse or deenergize the hoistmotor in unit 56,

as desired. I

In general, it will be evident that the invention is not confined to theparticular embodiment herein illustrated or to the details of suchembodiment, but may assume various forms. For example, any elevator orhoist mechanism which causes the stacking platform and the transferconveyors to be elevated differentially in order to 7 maintain the topof the stack of panels on the stacking platform even with or a desireddistance below the level of the transfer conveyors at all times may beemployed. That is the important thing, although the preferred manner ofimplementing it is that illustratedin which the hydraulic jack or othermeans supporting the stacking platform is mounted directly on theelevator means which carries the transfer conveyors. Another and perhapsmore obvious way of obtaining relative elevation of platform andtransfer conveyors would be by use ofa jack mounted stationarily andcoordinated with movement of the elevator carrying the conveyors.Likewise, other forms of transfer conveyors may be employed to removethe panels from the receiving rack and deposit them in a stack on theplatform.

Moreover, in connection with the manner in which the conveyors andstacking platform are elevated, it will be evident further that thehoist mechanism raising the elevator cage 44, hence the transferconveyor 42, need not be operated continuously, but may be caused tooperate by progressive increments, so that the transfer conveyors 44will be elevated in stages, stopping at each receiving rack shelf longenough to transfer the panel or panel group supported thereon to thestacking platform, and then moving up to the next shelf, etc. Likewise,the stacking platform supporting jack need not be lowered by incrementseach time a single panel or panel group is transferred to the stack, butmay be lowered in larger steps initiated with the reception each time onthe stack of an additional predetermined number of panels or layers.Alternatively, the stacking platform could be lowered relative to thetransfer conveyors at a generally constant rate, whether the transferconveyors were to be raised by increments or steadily. It is important,however, these two principal moving elements may be motivated, that thetop of the stack of panels be kept always belowthe level of the transferconveyors, but not so far below that level that the panels must dropexcessively in moving from the transfer conveyors to the top of thestack. Otherwise they might be damaged or become caught and obstructoperation of the system.

As a matter of convenience in removing the stack of panels from thestacking platform, I prefer to lay a group of skids or spacers lSB(Figures 2 and 6) on top the stacking platform to serve as the supportfor the panels thereon. These skids are oriented parallel to thedirectionof movement of the panels onto the stack, so that a lift truckor similar conveyance can pick up the stack by inserting its lift forkbeneath it.

I claim as my invention:

1. Panel stacking apparatus comprising a stacking platform, meansoperable to. deliver panels at depositing locations directly above saidplatform at various elevations for stacking on said platform, andplatform support means operable to adjust automatically the elevation ofsaid platform in relation to the height of the stack of panels on saidplatform and the elevation of the location for delivery of eachparticular panel by said delivery means, to dispose the top of the stacknot more than a predetermined small distance below each suchpanel'delivery location irrespective of the elevation thereof.

2. Panel stacking apparatus defined in claim 1, wherein the paneldelivery means comprises conveyor means operable to transfer panelsedgewise in a generally horizontal direction to the di livery location,and conveyor elevator means carrying said conveyor means and guided forvertical movement to vary the operating height thereof.

3. Panel stacking apparatus defined in claim 2, wherein the platformsupport means is carried by the conveyor elevator means.

4. Panel stacking apparatus defined in claim 2, wherein the platformsupport means is carried by the conveyor elevator means and comprises ahydraulic jack, and means controlling said jack to effect descent of theplatform by successive increments automatically in response tosuccessive panel deliveries by the conveyor means to the top of thestack on the platform.

5. Panel stacking apparatus comprising a stacking platform, apanel-supporting rack disposed adjacent to said stack-ing platform andhaving a vertical series of panel-receiving shelf spaces openingedgewise toward the space above said platform, panel conveyor meansoperable to engage and transfer a panel in the lowermost shelf space tothe platform for depositing the same thereon, said platform normallybeing disposde in elevation slightly below said lowermost shelf space,elevator means operable to elevate said conveyor means progressively soto engage and transfer, one after another, successively, panelssupported in the higher shelf spaces of said rackto the stack of panelson said platform, means supporting said platform and operable to lowerthe same relative to said conveyor means, and control means, actuatedautomatically in response to operation of said conveyor means totransfer a panel to the platform stack, to operate said platformsupporting means to lower said platform progressively relative to saidconveyor means during successive transfer of panels to the platformstack, in such manner that the top of said stack is maintained within apredetermined maximum distance below the conveyor means duringprogressive elevation thereof to engage and transfer the panels.

6. Panel stacking apparatus comprising a stacking platform, apanel-supporting rack disposed adjacent to said stacking platform andhaving a vertical series of panel-receiving shelf spaces openingedgewise toward the space above said platform, panel conveyor meansoperable to engage and transfer a panel in the lowermost shelf space tothe platform for depositing the same thereon, said platform normallybeing disposed in elevation slightly below said lowermost shelf space,elevator means operable to elevate said conveyor means progressively soto engage and transfer, one after another, successively, panelssupported in the higher shelf spaces of said rack to the stack of panelson said platform, hydraulic jack means carried by said elevator meansand supporting said platform, fluid actuating means for said jack,operable to lower said hydraulic jack and platform, and control means,actuated intermittently by operation of said conveyor means to transfera panel to the platform stack, to operate momentarily said fluidactuating means and thereby to lower said platform progressively byincrements during successive transfer of panels to the platform stack,in such manner that the top of said stack is maintained slightly belowthe conveyor means during progressive elevation thereof to engage andtransfer the panels.

7. Panel stacking apparatus defined in claim 6, wherein the fluidactuating means comprises a control valve, and the control meanscomprises a valve-operating means and a control member cooperating withsaid valve-operating means, said control member being mounted on theelevator means'for movement between a. lowered position resting on thetop panel on the platform stack, in which position said control memberand valve-operating means controlled thereby operatively position saidcontrol valve to restrain lowering of the hydraulic jack relative to theelevator means, and a raised position effected by transfer thereunder ofa succeeding panel to the top of the stack, to reposition said controlvalve for lowering of the hydraulic jack, the platform and the stack ofpanels thereon and said control member into the latters lowered positionto position said valve again in its jack-restraining position,incremental lowering of the hydraulic jack occurring in such manner witheach transfer of a panel to the stack.

8. Panel stacking apparatus defined in claim 6, wherein the fluidactuating means comprises a solenoid-controlled normally closedhydraulic relief valve, opening of which vents fluid from the loadedhydraulic jack to enable lowering of same by gravity, and closure ofwhich halts such lowering, and the control means operating said valvecomprises a switch and a switch-actuating member carried by the elevatormeans for movement thereon between opposite switch-actuating positionsand engageable by the top panel on the platform stack, said member beingmovable into one switch-actuating position to open the valve byengagement of such member by a panel transferred to the stack, toinitiate lowering of the hydraulic jack, and said member being movableoppositely to close said valve again after the jack, and thereby saidpanel engaged by said switchactuating member, has descended bysubstantially a panels thickness relative to the elevator means.

9. Panel stacking apparatus comprising a panel-supporting rack includinga plurality of supportin shelves arranged in vertical series therein,said rack having an open discharge end for edgewise removal of thepanels from the rack shelves, a stacking platform disposed adjacent tosaid racks discharge end, conveyor means cooperating with said rack,means operable to vary progressively the elevation of said conveyormeans in relation to the rack to transfer the panels generally edgewisefrom the different rack shelves, in successive order, to depositinglocations directly above said platform and for depositing thereon, andjack means operable to adjust automatically the elevation of saidplatform, and hence of the top of the stack thereon, relative to theelevation of the conveyor means, to locate the top of the 14 stack inpanel-receiving position at all times slightly below said conveyor meanselevation.

10. Stacking apparatus defined in claim 9, wherein the rack comprises anopen-ended framework, and the plurality of rack; shelves are supported,vertically arranged, by said framework, said shelve individuallycomprising a longitudinal member spaced from and between the sides ofsaid framework, transverse support members extending between theframework sides, a first one at a location generally between the ends ofthe rack, and another at a location spaced longitudinally therefrom, tosupport said longitudinal member projecting cantilever fashion from saidfirst transverse member in the direction away from the other transversemember, the projecting cantilever portions of the longitudinal membersof the plurality of shelves in the rack defining both longitudinal andvertical unobstructed opening therebetween, and further wherein theconveyor means comprises a plurality of belt conveyors movable in therack spaces adjacent to and between said longitudinal members.

11. Panel stacking apparatus comprising rack means for initiallysupporting a serie of substantially horizontally disposed panelsarranged in spaced superposed relationship, platform supporting meansmovable vertically incrementally distances corresponding to the verticalspacing between the panels of said series, a stacking platform disposedadjacent to said rack means, carried by said platform supporting meansand operable to receive thereon a stack of panels discharged from saidrack means, means operable to alter the vertical position of saidstacking platform relative to said platform supporting means to dis osethe top of the panel stack on said platform slightly below a panelsupported by said rack means in each incrementally adjusted position ofsaid platform supporting means irrespective of the height of the panelstack on said platform, and means operable to transfer said panelsindividually edgewise from said rack means into stacked position on saidplatform.

ALFRED FRANK PIERCE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,615,813 Romine Jan, 25, 1927 1,772,734 Romine Aug. 12, 19302,113,926 Pierce Apr. 12, 1938 2,181,357 Chipman Nov. 28, 1938 2,228,887Peterson Jan. 14, 1941 2,376,176 Neja May 15, 1945

